This issue relates to Office 365 only.

Project shows as progressing but the source estimate shows zero items and zero items are migrated even after the project has  been running for a while (over an hour). Please see example screenshot below.

This can occur when the server can see and access the mailboxes but is unable to calculate the source estimate count or start transferring content.

This can occur at times when using to connect to Office 365.  Please set the Office 365 connection to instead.